1. Field of the Invention
This invention relates to an armature winding assembled in an armature core, and more particularly to an armature winding of the so-called concentric wound type in which a plurality of coils having respectively different coil pitches are concentrically continuously wound around the armature axis to form each of a plurality of magnetic poles.
2. Description of the Prior Art
In an armature winding of the so-called concentric wound type, a plurality of coils having respectively different coil pitches are concentrically wound around the axis of each pole. These plural coils are continuously wound to form each of a plurality of magnetic poles. There are generally two methods for concentrically continuously winding such coils each of which has a coil pitch different from that of another. According to one of the methods, the coil having the longest coil pitch is wound first of all, the coils having successively shorter coil pitches being then successively wound in the above order, and finally the coil having the shortest coil pitch is wound. According to the other method, the winding sequence is reversed to that above described and is such that the coil having the shortest coil pitch is wound first of all, the coils having successively longer coil pitches being then successively wound in the above order, and the coil having the longest coil pitch is finally wound. Therefore, the plural continuously wound coils have a starting end at which the winding of the plural coils is started and a terminating end at which the winding of the plural coils is terminated. The conductor portions in the starting end and terminating end of the plural continuously wound coils will be called hereinafter terminal conductors to be distinguished from the remaining conductor portions of the coils. One of the terminal conductors is led out along one of the coil sides of the coil having the longest coil pitch, while the other terminal conductor is led out along one of the coil sides of the coil having the shortest coil pitch. Thus, when such coils are continuously wound in a concentric pattern to provide an armature winding assembled in a slotted armature core, a terminal conductor is led out necessarily from the coil having the shortest coil pitch as described above, and various objectionable problems as pointed out below have been inevitably encountered during the assembling of the plural coils in the slotted armature core due to the presence of such a terminal conductor.
After the step of assembling of the armature winding in the slotted armature core, it is necessary to shape the coil ends of the armature winding so that the coil ends can be configured to satisfy the predetermined dimensional requirement. This is generally mechanically done by the use of a set of shaping jigs together with a press such as a hydraulic press or a pneumatic press. It is to be noted in this case that the aforementioned terminal conductors of the armature winding assembled in the slotted armature core have no fixed figure. Therefore, when the coil ends are subjected to the mechanical shaping in such a state, the coil ends will be mechanically shaped in a condition in which the terminal conductors will be clamped between the armature core and one of the shaping jigs or they will be abnormally deformed. This will result in damage to or severing of the terminal conductors or coils. It has therefore been a conventional practice to guide the terminal conductors along the coil ends to a position at which the terminal conductors are not affected by the shaping jigs, and then, to carry out the mechanical shaping of the coil ends. In this case, the terminal conductor of the coil, which has the shortest coil pitch and is located radially innermost in the group of the concentrically arranged coils, is guided to ride across the coil ends of the remaining coils having the coil pitches different from its coil pitch in the coil group until it is brought to the position at which it is not affected by the shaping jigs. The terminal conductor guided to such a position will cross at substantially right angles the conductors forming the coil ends of the individual coils. When the coil ends are shaped in such a condition, a concentrated stress is imparted to the area in which this terminal conductor makes a point contact with the coil-end conductors. The coil ends mechanically shaped in the above condition have been defective in that the insulator layer covering the conductors tends to be damaged resulting in an objectionable reduction in the insulation of the coils. It has therefore been a conventional practice that such a terminal conductor is passed between the conductors forming the coil ends so as to minimize the number of cross points between this terminal conductor and the conductors forming the coil ends and is then guided to the position at which it is not affected by the shaping jigs. However, many man-hours have been inevitably required for the mechanical shaping of the coil ends due to the fact that such a step resorts to manual handling. In the case of the terminal conductor of the coil having the longest coil pitch, such a problem is not encountered since it can be led out without crossing the conductors forming the coil ends.